android - 如何在 fragment 中实现 onBackPressed() 和 Intent ？

Question

我知道 onBackPressed() 是 Activity 中的一种方法，但我想在 fragment 中使用该功能，这样当按下后退按钮时，它会通过 Intent 重定向到另一个 Activity 。有什么解决办法吗？

public class News_Events_fragment extends Fragment {
ProgressDialog pd;
ListView lv1;
SharedPreferences sharedPreferences = null;
int NotiCount;
TextView txt_title, txt_msg, textView;
Context context;
Intent intent ;
ArrayList<SliderMsgTitleModel> CurrentOfficersPastList;
NewsActivityAdapter pastAdapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    context = (Context) getActivity();

    View rootView = inflater.inflate(R.layout.activity_news, container, false);

    new AsyncTask<Void, Void, ArrayList<SliderMsgTitleModel>>() {

        protected void onPreExecute() {
            pd = new ProgressDialog(getActivity());
            pd.setCancelable(true);
            pd.setTitle("UPOA");
            pd.setMessage("Please wait,loading the data...");
            pd.show();
        }

        @Override
        protected ArrayList<SliderMsgTitleModel> doInBackground(
                Void... params) {
            System.out.println("In Background");
            CurrentOfficersPastList = new ArrayList<SliderMsgTitleModel>();
            // display view for selected nav drawer item
            ParseQuery<ParseObject> query = ParseQuery.getQuery("message");
            query.whereEqualTo("featured_status", true);
            // query.whereEqualTo("push_status", true);

            query.orderByDescending("updatedAt");

            query.selectKeys(Arrays.asList("title"));
            query.selectKeys(Arrays.asList("message"));
            try {
                query.setCachePolicy(ParseQuery.CachePolicy.NETWORK_ELSE_CACHE);
                List<ParseObject> results = query.find();
                for (int i = 0; i < results.size(); i++) {
                    ParseObject object = results.get(i);
                    CurrentOfficersPastList.add(new SliderMsgTitleModel(
                            object.getString("title"), object
                                    .getString("message")));
                    System.out.println("title is=="
                            + object.getString("title") + "&& message is"
                            + object.getString("message") + "size is"
                            + CurrentOfficersPastList.size());

                }
            } catch (Exception e) {
                e.getMessage();
            }
            pd.dismiss();

            return CurrentOfficersPastList;
        }

        @SuppressWarnings("unchecked")
        @Override
        protected void onPostExecute(ArrayList<SliderMsgTitleModel> value) {

            pd.dismiss();
            /*Intent ent = new Intent(getActivity(), NewsActivity.class);
            ent.putExtra("NEWSLIST", (ArrayList<SliderMsgTitleModel>) value);
            startActivity(ent);
            System.out.println("Value is" + value.size());*/

            CurrentOfficersPastList = new ArrayList<SliderMsgTitleModel>();
            CurrentOfficersPastList = value;
            lv1 = (ListView) getActivity().findViewById(R.id.list_title);
            pastAdapter = new NewsActivityAdapter(getActivity(), R.layout.activity_news_txt, CurrentOfficersPastList);
            lv1.setAdapter(pastAdapter);

        }
    }.execute();

    return rootView;
}

public void onBackPressed() {
    // TODO Auto-generated method stub
    //super.onBackPressed();
    //Toast.makeText(getApplicationContext(), "click",2000).show();
            String cameback="CameBack";
            intent = new Intent(getActivity(),HomeActivity.class);
            intent.putExtra("Comingback", cameback);
            startActivity(intent);
}

 }

Answer 1

您可以使用回调接口(interface)与 fragment 交互。在您的 Activity 中添加以下内容:

public class MyActivity extends Activity {

    protected OnBackPressedListener onBackPressedListener;

    public interface OnBackPressedListener {
        void doBack();
    }

    public void setOnBackPressedListener(OnBackPressedListener onBackPressedListener) {
        this.onBackPressedListener = onBackPressedListener;
    }

    @Override
    public void onBackPressed() {
        if (onBackPressedListener != null)
            onBackPressedListener.doBack();
        else
            super.onBackPressed();
    } 

    @Override
    protected void onDestroy() {
        onBackPressedListener = null;
        super.onDestroy();
    }
}

在您的 fragment 中添加以下内容:

public class MyFragment extends Fragment implements MyActivity.OnBackPressedListener {

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
         ((MyActivity) getActivity()).setOnBackPressedListener(this);
    }

    @Override
    public void doBack() {
        //BackPressed in activity will call this;
    }

}